Pupils who make false allegations against teachers should have details of that complaint kept on their school records, a union demanded.

The Association of Teachers and Lecturers (ATL) also called for "some legal process" by which falsely accused teachers could have their names cleared.

The union said the threat of bogus allegations was a constant fear among teachers and other members of staff, highlighting their vulnerability.

Union members voted unanimously, at the ATL's annual conference in Cardiff, to demand better measures to ensure children understood the cost of their actions - and faced legal action where necessary.

David Hytch from North Wales said teachers were vulnerable and a small minority of pupils were prepared to exploit that.

"There's still a problem and it's this - 'I can have your job, all I've got to do is get my mum to write a letter'," said Mr Hytch, quoting a comment made by a pupil to one of his colleagues.

After the case of head teacher Majorie Evans - who was suspended for 18 months before being cleared of assaulting a pupil - there was some political will to address the issue, Mr Hytch told delegates.

"But it's been open season on teachers for too long," he said.

'Cloud of suspicion'

Even when an accused teacher had been cleared of any wrongdoing, a cloud of suspicion hung over them, said Mr Hytch, with some parents saying they did not want that teacher to teach their child.

"What we need is some sort of legal power that enables it to be proved that the allegation made was malicious, deliberate and groundless," he said.

At present the only option available was to sue the pupil for defamation, which was highly expensive.

"The best they can achieve is that they are found not guilty at the end of a trial, and after a disciplinary procedure at a school the best they can achieve is no discipline being taken," said ATL solicitor Sharon Liburn.

Pupil power

The union does not seek to silence children with genuine complaints.

Its general secretary, Peter Smith, said pupils had discovered how easy it was to get a teacher suspended and knew what power they had over teachers' employment.

"Of course pupils must feel comfortable that they can whistle-blow, but if a pupil makes groundless and malicious accusations, disciplinary action must be applied to them and they should face possible expulsion," said Mr Smith.

"A teacher who has been falsely accused should not have to walk down the corridor and face the pupil who made the bogus claim," he said.

ATL regional officer Peter Jackson recalled how one union member was falsely accused of sexually assaulting two female pupils.

'Stitched up'

"Nine months later, after the shame, embarrassment and stress had been heaped on the teacher, his wife and their three teenage sons, he appeared at the crown court," said Mr Jackson.

"Over the next five days, ATL's counsel exposed the girls' conspiracy.

"How, on a particular day during the holiday, they had met and hatched a plan to stitch Teacher X up."

Every teacher ran the risk of being set up by malicious pupils, Mr Jackson said.

"Though they may eventually be cleared, the damage done is incalculable."